The equatorial electrojet (EEJ) is an intense electric current that flows in the ionosphere in a narrow zone above the magnetic dip equator during the daytime. The electrojet current produces a large enhancement of the surface component of the geomagnetic field at and in the vicinity of the dip equator. The EEJ is most intense around local noontime and appears to be more stable than other ionospheric current systems. This report presents a brief overview of the characteristics of the EEJ, including its location, electron density profile, current distribution, and magnetic field. In addition, the diurnal and seasonal variations of the EEJ are discussed. The relationship of the EEJ to the worldwide dynamo current system is discussed, in addition to a comparison with the aurora electrojet (AEJ). A derivation of the EEJ current distribution is presented that is based on an anisotropic conductivity model of the ionosphere. A summary of several experiments involving the generation of low4requency signals from a heated and modulated EEJ is also given. It is anticipated that this report will provide helpful background information to scientists and engineers engaged in the development of future experiments that involve the transmission of signals in the ELF and VLF frequency bands from a heated and modulated EEJ.